It is desirable to have a television receiver which is capable of receiving not only television signals, but also broadcast FM radio signals. In the United States, the broadcast FM band occupies a band of frequencies extending from approximately 88 MHz to approximately 108 MHz. This band of frequencies lies between the frequencies allocated for broadcast television channel 6 and television cable channel 98. Modern intercarrier-sound-type television receivers having the capability to receive broadcast FM signals are known from the prior art. However, in these known arrangements, their respective manufacturers added a separate FM radio having its own tuner. This may have been done because television tuners commonly include tuned circuits (FM traps) for trapping out FM signals which may otherwise interfere with television signal reception.
Another reason for utilizing a separate tuner for the FM radio is that the full gain of the television RF amplifier stage is too great for properly amplifying received FM radio signals. Automatic gain control (AGC) of the RF amplifier stage of a television receiver is derived from the video intermediate frequency (IF) amplifier stage, which would provide meaningless signals in FM radio mode. Operating the RF stage of the television tuner at maximum gain would cause overload of the RF stage on strong signals. The addition of a separate FM radio AGC system for controlling the RF stage of the television receiver is too costly and complex to be a practical solution.